A colonoscopy is the visual examination of a patient's colon from a remote location through the use of instrumentation. In examining the colon, an instrument known as a colonoscope is used. The colonoscope is provided a sensing tube having optical means and insufflation means, and an observation and control unit that is connected to one end of the sensing tube. During the colonoscopy, the sensing tube is inserted into the colon via either the anus or a stoma in the patient's abdominal wall and the colon is inflated with the insufflation means to aid the surgeon's examination. In the past, surgeons have relied exclusively upon the sphincter muscles ringing the anus to provide a seal around the sensing tube. This seal is necessary to maintain the colon in an inflated condition and prevent the discharge of fecal material during the examination. However, the sphincter muscles relax after the administration of sedation and in older patients, thus reducing the seal around the colonoscope sensing tube and increasing the difficulty of the examination. In an examination through a stoma, there are no sphincter muscles to provide a seal.